[402] Cytology-Histology Correlation of Mucinous Nonneoplastic Cyst of the Pancreas.

Xiaoqi Lin, Ritu Nayar, Bing Zhu. Northwestern University, Chicago

Background: A recently described mucinous nonneoplastic cyst (MNNC) of the pancreas is defined as cysts lined by mucinous epithelium and supported by hypocellular stroma without communication with pancreatic ducts. It is important to recognize MNNC since its management and prognosis are different from mucinous cystic neoplasm (MCN) and intraductal papillary mucinous neoplasm (IPMN). FNA cytomorphology of MNNC has not been described.
Design: 24 MNNCs diagnosed on surgical resection were retrieved. 18 had pre-surgery EUS-FNA biopsy. FNA cytomorphology and surgical histology were evaluated and correlated. Cyst fluid CEA and amylase concentrations were retrieved.
Results: FNA diagnoses included suspicious for adenocarcinoma (1 case), IPMN (1), suggestive of MCN (4), mucinous lesion (2), atypical (2), benign glandular cells (4), and unsatisfactory (4). FNA cytology showed flat honeycomb sheets/nests of cuboidal or columnar cells. Papillary architecture was seen in 2 cases, and abundant single cell pattern in 1. Goblet cells were sen in 18%. Cytoplasm was delicate or vacuolated (64%). Nuclei were round or oval and small to slightly enlarged with 1 or 2 inconspicuous nucleoli (prominent in 1 case), fine granular chromatin, and smooth nuclear contour (irregular in 1 case). Nuclear grooves and nuclear pseudoinclusons seen in 46% and 27%. Most cases showed watery mucin (thick mucin in 2). CEA ranged from 75.2 to 5,488 ng/ml and amylase from 19 to 28,478 U/L.
On surgical resection, MNNCs were randomly located in pancreas and were either unilocular or multilocular cysts lined by a single layer of bland columnar or cuboidal mucinous cells. Papillary structure was seen in 21% The glandular epithelial cells were diffusely positive for CK7 (100%), CD99 (basally, 100%) and PDX-1 (66%), focally positive for CD10 (superficial, 67%), CDX-2 (19%) and CK20 (6%), and negative for MUC2. Stromal cells in the cyst wall were focally, weakly positive for ER or PR (6%) and negative for inhibin.
Conclusions: MNNC shares clinical, radiologic and FNA cytology features with MCN and IPMN. Demonstration of communication with pancreatic ducts by radiology and IHC for CDX-2 and MUC2 (data not shown) are helpful to distinguish MNNC from IPMN. IHC for ER, PR and inhibin on cellblocks/needle cores is helpful to distinguish MNNC from MCN, however, IHC for MUC2, CDX-2, PDX-1, CK7, CK20, CD10, and CD99 is not useful (data not shown). Measurement of CEA and amylase is not useful. Combination of FNA cytology and IHC on cellblock/core biopsy along with clinical presentation and imaging studies is critical to diagnose MNNC on EUS-FNA and distinguish it from IPMN and MCN.
Category: Cytopathology

Tuesday, March 1, 2011 9:30 AM

Poster Session III # 62, Tuesday Morning


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